rails.md

description	Rails conventions for .rb and .erb files
globs	**/*.rb **/*.erb

Rails Rules

MVC Structure

• Follow "fat models, thin controllers". Business logic lives in models or service objects, not controllers.
• Controllers are responsible only for: parsing params, calling the right service/model method, and rendering a response.
• Views contain no business logic. Extract helpers for non-trivial view computations.

Models

• Validate all user-supplied data at the model level using ActiveRecord validations.
• Use scopes (not class methods) for reusable query fragments: scope :active, -> { where(active: true) }.
• Extract shared model behavior into concerns under app/models/concerns/.
• Use before_action and callbacks sparingly. Prefer explicit service calls over hidden callbacks.

Controllers

• Use strong parameters with require and permit for every action that accepts user input.
• Keep each action to roughly ten lines. Extract longer logic into service objects.
• Follow RESTful routing. Create new controllers for non-CRUD actions rather than adding custom actions to existing controllers.

Service Objects

• Place service objects in app/services/. One class per operation (e.g., UserRegistrationService).
• Give service objects a single public method (call or a descriptive verb).
• Return a result object or raise a domain exception. Never return raw ActiveRecord objects from a service that does complex logic.

Internationalization

• Use I18n for all user-facing strings. Never hard-code English text in views or mailers.
• Keep locale files organized by feature, not by model.

Security

• Never trust user input. Always use parameterized queries (ActiveRecord does this by default).
• Avoid html_safe and raw in views unless the content is known to be safe.
• Use authenticate_user! (Devise) or equivalent before actions that require authentication.